JPH07165696A - Production of bis(isocyanatomethyl)cyclohexane - Google Patents

Abstract

PURPOSE:To provide a production method simplified in process, capable of reducing utility cost and, simultaneously, capable of obtaining bis(isocyanatomethyl)cyclohexane in high selectivity and high space time yield. CONSTITUTION:One mol of bis(aminomethyl)cyclohexane is reacted with 2-3.5mol of dimethyl carbonate in the presence of a basic catalyst and unreacted dimethyl carbonate is recovered as an azeotropic mixture with methanol and directly recycled to a raw material system. The resultant bis(methoxycarbonylaminomethyl)cyclohexane is thermally decomposed under reduced pressure using a cobalt, nickel or iron catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing bis (isocyanatomethyl) cyclohexane from bis (aminomethyl) cyclohexane and dimethyl carbonate. Bis (isocyanatomethyl) cyclohexane is a compound useful as a raw material for producing polyurethane, polyurea and the like having excellent light resistance.

[0002]

2. Description of the Related Art Bis (isocyanatomethyl) cyclohexane is industrially produced by the reaction of bis (aminomethyl) cyclohexane with phosgene. This current phosgenation method has problems in the treatment of by-product hydrochloric acid, handling of highly toxic phosgene, corrosion of equipment, etc., and in recent years, it is a safer and more economical alternative to bis (isocyanate). Development of an industrial production method of (methyl) cyclohexane is desired.

As a method for producing an isocyanate starting from an amine compound, there is known a method of synthesizing a urethane compound in the first reaction step and then thermally decomposing the urethane compound in the second reaction step to obtain an isocyanate compound. ing.
Various methods have been proposed for producing a urethane compound from an amine compound in the first reaction step. JP 59
No. 1725451 discloses an oxidative carbonylation method of producing a urethane compound by reacting an amine compound with carbon monoxide and molecular oxygen or a nitro compound in the presence of alcohol. This method uses an expensive platinum group catalyst such as Pd and Rh, and since it has no choice but to react under high temperature and high pressure, there is a drawback in that the catalyst cost and the equipment construction cost increase industrially. JP-A-56-169665 proposes a method for producing a urethane compound by reacting an amine compound with a carbamic acid ester or an amine compound with urea and an alcohol. Since this method requires the presence of a large amount of alcohol, the space-time yield is small, and a large amount of by-products derived from carbamic acid ester or urea is generated, which requires a complicated operation for separating and recovering the urethane compound. There is a drawback of.

A method for producing a urethane compound by reacting an amine compound with a carbonic acid ester has also been proposed. In this reaction, Japanese Patent Publication No.
A b-type Lewis acid catalyst, an organic tin catalyst in JP-A-55-4316, and a catalyst composed of Pb, Ti, Zr and the like in JP-A-57-82361 are disclosed. However, according to these examples, the reaction rate is generally low, and the catalyst separation is expensive and uneconomical. In addition, JP-A-54-16
No. 3527 discloses a method for producing an aromatic urethane from an aromatic amine compound and a carbonic acid ester in the presence of a basic catalyst such as a metal alcoholate or a nitrogen-containing heterocyclic compound. In this case, a large amount of by-products are generated by the N-alkylation reaction and the aromatic urethane yield is low.

Japanese Unexamined Patent Publication (Kokai) No. 64-85956 discloses a method for producing a urethane compound by reacting an aliphatic amine compound with a carbonic acid ester, which suppresses a dimerization reaction which is a side reaction in the presence of an alkali catalyst. Therefore, in particular, a method is proposed in which the amount of dimethyl carbonate used is at least 4 times the molar ratio of the diamine (8 to 16 times the molar ratio in the examples), and the water content in dimethyl carbonate is less than 0.2%. However, when bis (methoxycarbonylaminomethyl) cyclohexane is produced from bis (aminomethyl) cyclohexane and dimethyl carbonate by this method, when the reaction is carried out at a dimethyl carbonate / diamine molar ratio of 4 or more, the reaction product solution is Remains unreacted dimethyl carbonate in a molar ratio of 2 or more. This dimethyl carbonate and the produced methanol have an azeotropic relationship (an azeotropic composition under normal pressure; a dimethyl carbonate: methanol = 3: 7 weight ratio). Therefore, the unreacted dimethyl carbonate is recovered in a complicated separation operation and its utility. It has the drawback of being expensive. On the other hand, when unreacted dimethyl carbonate is azeotropically circulated and used as it is in the raw material system, the system is diluted with a large amount of methanol, and the catalyst amount must be increased in order to maintain a high yield. Space-time yield is also reduced.

Various proposals have been made for the thermal decomposition method of urethane compounds in the second reaction step. There are a vapor phase method and a liquid phase method for the thermal decomposition method of the urethane compound. Generally, it is said that the vapor phase method is a high temperature reaction and its endothermic reaction heat is large, so that it is difficult to design a reactor and it is not practical. On the other hand, the liquid phase method is carried out at a lower temperature than the gas phase method, but the thermal decomposition rate is low without a catalyst. Therefore, in order to increase the thermal decomposition rate and obtain isocyanate in high yield, various catalysts, solvents, stabilizers, and methods such as the use of carrier agents for the purpose of preventing recombination of isocyanate and alcohol once formed have been proposed. ing.

That is, JP-A-51-19721 and JP-B-57-45736 disclose periodic tables IB and II.
B, IIIA, IVA, IVB, VA, VB, VIA, VIIA and VIII elements, eg Mo, V, Mn, F
e, Co, Cr, Cu, Ni, Zn, Al, Sn, Ti
There is disclosed a method in which a large number of simple metals or organic and inorganic compounds composed of, etc. are used as a catalyst and the method is carried out under pressure, normal pressure or reduced pressure. In all cases, only examples of aromatic urethane compounds having high thermal decomposability are described. The thermal decomposability of urethane compounds and the stability of the formed isocyanate differ depending on their chemical structure, and the catalytic action is not uniform. A method for producing an aliphatic isocyanate is disclosed in Japanese Patent Laid-Open No.
No. 4-85956 describes Mn, Mo, and
A method of using one or more simple metals selected from W, Zn and Be or a compound of the metals is disclosed. Further, JP-A-62-238255 discloses a method for producing isophorone diisocyanate, which uses SnO ₂ or CuO and a mixture thereof as a catalyst in the absence of a solvent. However, when using these catalysts in the thermal decomposition method of bis (methoxycarbonylaminomethyl) cyclohexane, which is an aliphatic urethane compound and has low reactivity,
Insufficient in terms of reaction rate or yield.

[0008]

As described above, in the first reaction step and the second reaction step, when the bis (isocyanatomethyl) cyclohexane is produced by the conventional method, the reaction rate and the yield are not sufficient. Moreover, there are problems in the treatment method of unreacted dimethyl carbonate, catalyst cost, equipment cost, and the like. It is an object of the present invention to provide a process for the economical production of bis (isocyanatomethyl) cyclohexane from bis (aminomethyl) cyclohexane without the use of toxic phosgene.

[0009]

Means for Solving the Problems The inventors of the present invention have earnestly studied the industrial production method of bis (isocyanatomethyl) cyclohexane having the above-mentioned problems, and as a result, in the presence of a basic catalyst, bis (aminomethyl) ) If cyclohexane and dimethyl carbonate are reacted in a molar ratio within a specific range, a sufficient reaction rate can be obtained at an economical catalyst cost even if unreacted dimethyl carbonate is circulated as it is in an azeotropic composition with methanol, and Bis (methoxycarbonylaminomethyl) cyclohexane can be obtained in high yield as a homogeneous solution. Furthermore, if this urethane compound is pyrolyzed by reactive distillation in the presence of a specific catalyst, bis (isocyanatomethyl) cyclohexane is highly selected. The present invention has been completed by finding that it can be obtained with high yield and high space-time yield.

That is, according to the present invention, when bis (isocyanatomethyl) cyclohexane is produced by thermally decomposing bis (methoxycarbonylaminomethyl) cyclohexane obtained by the reaction of bis (aminomethyl) cyclohexane and dimethyl carbonate, ) In the presence of a basic catalyst, the reaction is carried out in the range of 2-3.5 molar ratio of dimethyl carbonate to 1 mol of bis (aminomethyl) cyclohexane, and unreacted dimethyl carbonate is recovered as an azeotropic composition with methanol and used as it is as a raw material. First reaction step of circulating use in the system, (b) an inert solvent having a boiling point higher than that of bis (isocyanatomethyl) cyclohexane, and one or more metal simple substances selected from cobalt, nickel and iron or the presence of the metal compound catalyst The bis (methoxycarbonylaminomethyl) cyclohexane obtained in the first reaction step was added to 350 ° C temperature, 1-500
A method for producing bis (isocyanatomethyl) cyclohexane, which comprises a second reaction step in which methanol and bis (isocyanatomethyl) cyclohexane produced by pyrolysis under reduced pressure of mmHg are separately recovered outside the system. is there.

The first reaction step and the second reaction step of the present invention are:
It is shown by the following reaction formula.

[Chemical 1]

Bis (aminomethyl) cyclohexane, which is a main raw material in the first reaction step of the present invention, has three kinds of isomers, and 1,3-form and 1,4-form are useful. These main raw materials are industrially produced by nuclear hydrogenation of 1,3- and 1,4-xylylenediamine. Dimethyl carbonate, which is an auxiliary material, may be a commercially available product as it is, or may be purified if necessary before use. It is preferable to remove water as much as possible from these raw materials in order to reduce the catalyst and maintain the activity. The amount of dimethyl carbonate used in the present invention is in the range of 2-3.5 mol ratio, preferably 2-3.0 mol ratio, relative to 1 mol of bis (aminomethyl) cyclohexane. When dimethyl carbonate is used in an amount of more than 3.5 mol and unreacted dimethyl carbonate is circulated and used as it is in an azeotropic composition with methanol,
Since the reaction system is diluted with a large amount of methanol, the amount of catalyst increases and the space-time yield also decreases. Further, when the unreacted dimethyl carbonate is combined with atmospheric distillation and pressure distillation, separated by extractive distillation and used in circulation, equipment cost and catalyst cost increase. On the other hand, if the amount used is less than 2 mol ratio, unreacted bis (aminomethyl) cyclohexane remains, which is not economical.

The basic catalyst used in the first reaction step includes alkali metal or alkaline earth metal alcoholates and strongly basic anion exchange resins.
Specific examples of the alcoholates include methylates such as sodium, potassium, lithium, calcium and barium,
Examples include ethylate. Practically, sodium methylate is preferable from the economical viewpoint, and sodium methylate / methanol solution which is commercially available is most preferable. In the case of sodium methylate, the amount of the catalyst used is 0.05 to 5% by weight, preferably 0.1 to 2% by weight, as the solution concentration of the reaction solution. If the amount of sodium methylate used is less than 0.05% by weight, a sufficient reaction rate cannot be obtained, and if the amount used is more than 5% by weight, the catalyst cost increases, which is not economical.

The strong basic anion exchange resin used in the first reaction step is a resin having a crosslinked structure as a base material and a strong basic anion introduced therein. As the matrix of the resin, styrene-divinylbenzene-based crosslinked polystyrene, acrylic acid-based polyacrylate, or a heat-resistant aromatic polymer into which an ether group or a carbonyl group is introduced is used. Amino groups, substituted amino groups, quaternary ammonium groups, and the like are generally known as anion exchange groups in ion exchange resins, but in the case of strongly basic anion exchange resins, anion exchange groups are Among the quaternary ammonium, those introduced with a trialkyl-substituted nitrogen atom —N (R) ₃ and those introduced with a dialkylethanolamine cation such as —N (CH ₃ ) ₂ (C ₂ H ₄ OH) are used. , For example, Levatit M50
0, Levatit MP500, Levatit M504, Diaion PA306, Amberlyst A-26, Dowex TG550A and the like. The amount of these strongly basic anion exchange resins used in the case of batch reaction is in the range of 1 to 90% by weight, preferably 10 to 50% by weight as the concentration of the reaction solution.
It is in the range of% by weight. If the amount used is less than 1% by weight, a sufficient reaction rate cannot be obtained. If the amount used is more than 90% by weight, the catalyst cost increases, which is not economical.

The reaction rate can be improved by adding methyl formate in the first reaction step. Therefore, by adding methyl formate, it is possible to reduce the amount of catalyst used such as alkali metal or alkaline earth metal alcoholate. The amount of methyl formate added is in the range of 0.01 to 5 mol ratio, preferably 0.1 to 1 mol ratio, relative to 1 mol of bis (aminomethyl) cyclohexane. When the amount of methyl formate added is less than 0.01 mol ratio, the reaction accelerating effect is small, and when it is more than 5 mol ratio, the space-time yield decreases, which is not preferable.

In the first reaction step, since the urethane compound can be handled as a homogeneous solution, no particular solvent is required, but an inert solvent can also be used. Specific examples of the inert solvent include alcohols such as methanol and ethanol, ethers such as tetrahydrofuran and dioxane, and hydrocarbons such as benzene and toluene.

In the first reaction step, the reaction temperature is 0 to 150 ° C.
The reaction can be carried out under normal pressure or increased pressure within the range. Practically, it is preferable to carry out the reaction at a reaction temperature of 20 to 90 ° C. under normal pressure. The reaction operation can be carried out by an ordinary batch system and flow system. When conducting a homogeneous reaction using an alcoholate catalyst in the flow system, bis (aminomethyl)
By supplying cyclohexane, dimethyl carbonate, an alcoholate catalyst, and, if necessary, methyl formate to the reactor for reaction, a urethane compound can be obtained with a sufficient reaction rate and a good yield. In the case of a heterogeneous reaction with a strongly basic anion exchange resin catalyst, bis (aminomethyl) cyclohexane, dimethyl carbonate and, if necessary, methyl formate are supplied to a reaction tube previously filled with an ion exchange resin catalyst to react. be able to.

The reaction product solution from the first reaction step is neutralized,
Each component can be separated and recovered by a combination of filtration, distillation, evaporation, extraction, washing, crystallization and the like. The concrete example is as follows. First, the basic catalyst in the reaction product solution is neutralized with an acid, and the produced sodium salt is separated by filtration. As the acid, mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid can be used. Unreacted dimethyl carbonate is recovered as an azeotrope with methanol by distillation of the mother liquor and recycled to the raw material system. Therefore, the process of separating the unreacted dimethyl carbonate from the azeotropic methanol can be omitted, and the utility cost required therefor can be saved. On the other hand, the produced urethane compound can be recovered by distilling or evaporating the entire amount of methanol. When the urethane compound needs to be further purified, it can be carried out by an ordinary method, for example, with or without solvent, washing with water, crystallization treatment and the like.

In the second reaction step, the urethane compound bis (methoxycarbonylaminomethyl) cyclohexane obtained in the first reaction step is thermally decomposed in the presence of a specific solvent and a catalyst to give bis (isocyanatomethyl). Cyclohexane and methanol are obtained. As the solvent used in the second reaction step, a solvent having a higher boiling point than that of the produced bis (isocyanatomethyl) cyclohexane is used in order to selectively remove the vapor of the produced bis (isocyanatomethyl) cyclohexane from the system. Especially, a solvent having a boiling point difference of 40 ° C. or higher is preferable. Specific examples of the solvent include dioctyl phthalate, didecyl phthalate, esters such as didodecyl phthalate, dibenzyltoluene, pyrene, triphenylmethane, phenylnaphthalene, benzylnaphthalene, etc. Group hydrocarbons are mentioned. The amount of the solvent used was 0.2 with respect to bis (methoxycarbonylaminomethyl) cyclohexane.
It is in the range of 05 to 20 times by weight, preferably 0.1 to 10 times by weight.

The catalyst used in the second reaction step is a simple substance of one or more of the metals selected from cobalt, nickel and iron and the metal compound, and the soluble metal compound is preferable. Examples of such metal compounds include formic acid,
Examples thereof include metal salts of organic acids such as acetic acid, oxalic acid, naphthenic acid and benzoic acid, for example, metal chelating agents composed of β-diketone such as acetylacetone and benzoylacetone. Specifically as the catalyst of the second reaction step, cobalt acetate, cobalt benzoate, cobalt naphthenate, cobalt acetylacetonate, nickel acetate, nickel benzoate, nickel naphthenate, nickel acetylacetonate, iron acetate, iron benzoate, Examples thereof include iron naphthenate and iron acetylacetonate, which are industrially easily available and are preferably used. The amount of the metal compound used for the catalyst is 1 to 10 as the weight concentration of the metal with respect to the reaction solution.
It is in the range of 00 ppm, preferably in the range of 10 to 500 ppm.

The reaction temperature in the second reaction step is 150 to 350.
C., preferably 200 to 300.degree.
At a reaction temperature lower than 150 ° C, the rate of thermal decomposition of the urethane compound is low, and at a reaction temperature higher than 350 ° C, by-products increase, which is not preferable. The reaction pressure is a pressure at which bis (isocyanatomethyl) cyclohexane and methanol can be vaporized corresponding to the above reaction temperature, and usually 1 to
It is in the range of 500 mmHg. The produced mixed vapor of bis (isocyanatomethyl) cyclohexane and methanol is taken out of the system in a reactive distillation system and is decompressed by utilizing the difference in respective condensation temperatures. The reaction time varies depending on the type and amount of catalyst, reaction temperature, reaction pressure, reaction type, etc., but is usually in the range of 0.2 to 5 hours.

The reaction operation can be carried out by a batch system, but in practice, a flow system using a complete mixing reactor or a tubular reactor is preferable. In the flow system, for example, a multistage distillation column is used as a reactor, and a uniform solution consisting of bis (methoxycarbonylaminomethyl) cyclohexane, an inert solvent and a catalyst is continuously supplied to the reactor, and monoisocyanate is refluxed. Bis (isocyanatomethyl) while separating
Cyclohexane and methanol are extracted from the system and condensed. On the other hand, a predetermined amount of the retained liquid is continuously withdrawn from the reactor, the Hartz component is removed by an evaporator or the like, and then recycled to the raw material system. A high-purity product can be easily obtained by further rectifying this bis (isocyanatomethyl) cyclohexane fraction.

Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these implementations.

<First Reaction Step> Example 1 1,3-bis (aminomethyl) cyclohexane (1,3-BAC
Abbreviation) 129 g (0.9 mol), dimethyl carbonate (D
MC (abbreviated as MC) 180 g (2.0 mol) was charged into a 500 ml four-necked flask equipped with a reflux condenser, a thermometer, a nitrogen blowing nozzle, a separating funnel, and a stirring stirrer, and after nitrogen substitution, the temperature was changed. It was installed in a water bath adjusted to 50 ° C. When the temperature of the liquid in the reactor reached 50 ° C., 7 g of a 28% methanol solution of sodium methylate (NaOMe) (NaOMe; 0.036 mol) was dropped into the reactor from a separating funnel. The preparation condition at this time is D
MC / 1,3-BAC = 2.22 molar ratio, NaOMe / 1,3-
BAC = 0.04 molar ratio. After the completion of dropping the catalyst, the temperature of the reactor liquid was raised to 70 ° C., and the mixture was reacted under reflux for 2 hours. The reaction product solution was a homogeneous solution. A part of the reaction product solution was sampled, neutralized with phosphoric acid, and then analyzed by the internal standard method of gas chromatography. As a result, 1,3-
The yield of 1,3-bis (methoxycarbonylaminomethyl) cyclohexane (abbreviated as 1,3-BUC) based on BAC is 98.
It was 2%. Next, assuming the process of recycling unreacted DMC, the following experiment was conducted.

The reaction product solution obtained under the same conditions as above was charged into a distillation column, and the whole amount of unreacted DMC was recovered as an azeotropic composition with methanol. This recovered liquid is DMC: methanol =
It was a 3: 7 weight ratio. 1,3-BAC129g (0.9m
ol), 162 g (1.8 mol) of DMC and the recovered unreacted DMC solution (including 48 g of methanol) were charged into the above reactor. After 7 g of 28% methanol solution of sodium methylate (NaOMe; 0.036 mol) was added dropwise, the reaction was carried out under the same conditions as above. The reaction product solution was a homogeneous solution, and the yield of 1,3-BUC based on 1,3-BAC was 98.7%.

Examples 2 to 5 are based on the premise that unreacted DMC is recovered as an azeotropic composition with methanol and recycled as it is to the raw material system, and an experiment in which excess DMC and methanol corresponding to the azeotropic composition are added in advance. I went.

Example 2 129 g (0.9 mol) of 1,3-BAC, 180 g of DMC
(2.0 mol), 42 g of methanol (1.31 mo
1) and 55 g (0.9 mol) of methyl formate were charged into a reactor, and in the same manner as in Example 1, 3.5 g of a 28% methanol solution of sodium methylate (NaOMe; 0.0
(18 mol) was added dropwise and the mixture was reacted under reflux for 2 hours. The charging conditions at this time are DMC / 1,3-BAC = 2.22 molar ratio, NaOMe / 1,3-BAC = 0.02 molar ratio, and methyl formate / 1,3-BAC = 1 molar ratio. The obtained reaction product solution was a homogeneous solution, and the yield of 1,3-BUC based on 1,3-BAC was 95.4%.

Example 3 1,3-B was placed in a 50 ml four-necked flask equipped with a reflux condenser, a thermometer, a nitrogen blowing nozzle and a stirring stirrer.
AC 2.8g (0.02mol), DMC 5.3g
(0.06 mol), 4.1 g of methanol (0.13 m
ol), 1.2 g (0.02 mol) of methyl formate and 10 m of a strongly basic anion exchange resin (Levacit M504).
1 was charged and reacted under reflux at a reaction temperature of 60 ° C. for 6 hours. The charging conditions at this time are DMC / 1,3-BAC = 3 molar ratio and methyl formate / 1,3-BAC = 1 molar ratio. The resulting reaction product solution was a homogeneous solution, which was 1,3-BAC standard 1,3-
The yield of BUC was 97.1%.

Example 4 In the same manner as in Example 1, 129 g of 1,4-BAC (0.9
mol), 180 g (2.0 mol) of DMC and 42 g (1.31 mol) of methanol, and then 7 g (0.036) of a 28% methanol solution of sodium methylate.
(mol) was added dropwise, and the mixture was reacted under reflux at a reaction temperature of 70 ° C. for 2 hours. The resulting reaction product solution was a homogeneous solution,
The yield of 1,4-BUC was 96.4% based on BAC.

Example 5 A 1,3-BUC synthesis experiment was carried out by a flow system using a glass jacketed reaction tube (40ΦX500,670 ml). Warm water at 70 ° C was circulated in the reaction tube jacket. 1,3-BAC 150g / h, DMC21 using plunger pump
0.4 g / h, 51.3 g / h of methanol and 53.9 g / h of 28% methanol solution of sodium methylate were introduced from the lower part of the reaction tube, and the reaction product solution was extracted from the upper part of the reaction tube and collected. . The charging conditions at this time were DMC / 1,3-BAC = 2.2 molar ratio, NaOMe /
The ratio of 1,3-BAC is 0.04. After the steady state was reached, the reaction product was analyzed by gas chromatography, and the yield of 1,3-BUC based on 1,3-BAC was 95.7%.
Met.

Comparative Example 1 In a reactor similar to that of Example 1, 129 g of 1,3-BAC (0.
9 mol) and DMC 325 g (3.6 mol) were charged, and then 28% methanol solution of sodium methylate 7
g (NaOMe; 0.036 mol) was added dropwise and the reaction temperature was 7
The reaction was carried out at 0 ° C for 2 hours. The preparation conditions at this time are DMC
/ 1,3-BAC = 4 molar ratio, NaOMe / 1,3-BAC =
The molar ratio is 0.04. The obtained reaction product solution was a homogeneous solution, and the yield of 1,3-BUC based on 1,3-BAC was 94.3.
%Met. Next, assuming the process of recycling unreacted DMC, the following experiment was conducted. That is, unreacted D
When MC recycling is repeated, unreacted DMC
The amount of methanol entrained in the water increases and eventually unreacted D
The azeotropic composition of MC and methanol is circulated. Therefore, an addition experiment of methanol corresponding to the azeotropic composition was performed on unreacted DMC.

1,3-BAC129g (0.9g), DMC
325 g (3.6 mol) and 378 g of methanol (azeotrope composition amount with unreacted DMC) were charged into the reactor. 7% of 28% methanol solution of sodium methylate (NaO
Me; 0.036 mol) was added dropwise, and the reaction was performed under the same conditions as above. The reaction product solution is a homogeneous solution,
The yield of 1,3-BUC based on BAC was 81.3%.
Comparing this with Example 1, DMC / 1,3-BAC (molar ratio) was increased from 2.22 to 4.0 to cause reaction, and unreacted DMC was recovered in an azeotropic composition with methanol and was used as it was. It can be seen that when the raw material is used, the recycled amount of methanol is significantly increased and the 1,3-BUC yield is decreased in the second reaction.

<Second Reaction Step> Example 6 The catalytic decomposition performance was evaluated by measuring the thermal decomposition rate of 1,3-BUC in a reactive distillation type similar to that of an actual apparatus. Capillary, thermometer,
A 300 ml four-necked flask equipped with a reaction solution sampling nozzle and a fractionating head with a reflux condenser was used in the reactor. A receiver is attached to the fractionating head, and the reflux condenser is 60 ° C.
Of warm water. The upper part of the reflux condenser and the receiver were connected to a vacuum line through a cold trap cooled with methanol / dry ice. The reaction solution sampling nozzle was separately connected to a vacuum line through a receiver. 1,3-in the flask
15 g of BAC, 150 g of Marlotherm S (main component; dibenzyltoluene) solvent and iron acetylacetonate [F
e (AA) ₃ ] was charged to the solvent at 200 ppm,
After the atmosphere was replaced with nitrogen, the pressure in the system was reduced to 30 mmHg.
Next, the flask was placed in an oil bath maintained at a temperature of 265 ° C, and the reaction was started when the temperature in the flask reached 260 ° C. After the start of the reaction, the reaction solution was sampled every predetermined time and the composition was analyzed by gas chromatography. As a result, the thermal decomposition rate k ₁ was calculated when the thermal decomposition reaction of 1,3-BUC was a primary reaction of 1,3-BUC concentration. The results are shown in Table 1.

Examples 7 to 9 In the same manner as in Example 6, cobalt acetylacetonate [Co (AA) ₂ ] and cobalt acetate [Co (CH ₃ CO 2
O) ₂ .4H ₂ O] and nickel acetylacetonate [Ni (AA) ₂ ] were added to the Marlotherm S solvent in an amount of 200 ppm to carry out a thermal decomposition reaction to obtain 1,3-B.
The thermal decomposition rate k ₁ of UC was determined. The results are shown in Table 1.

Comparative Examples 2 to 9 In the same manner as in Example 5, no catalyst (Comparative Example 2), titanium oxide acetylacetonate [TiO (AA) ₂ ] (Comparative Example 3), zirconium acetylacetonate [Zr ( A
A) ₄ ] (Comparative Example 4), chromium acetylacetonate C
r (AA) ₃ (Comparative example 5), Aluminum acetylacetonate [Al (AA) ₃ ] (Comparative example 6), Copper acetylacetonate [Cu (AA) ₂ ] (Comparative example 7), Manganese acetylacetonate [ _{Mn (AA) 2 · 2H 2} O ]
(Comparative Example 8) and molybdenum acetylacetonate [MoO ₂ (AA) ₂ ] (Comparative Example 9) were subjected to a thermal decomposition reaction to determine the thermal decomposition rate k ₁ of 1,3-BUC. The results are shown in Table 1.

[0036]

[Table 1] Type of catalyst Thermal decomposition rate [h ^-1 ] Comparative example 2 No catalyst 0.145 Example 6 Fe (AA) ₂ 4.53 Example 7 Co (AA) ₂ 4.39 Example 8 Co ( CH ₃ COO) ₂ 4H ₂ O 4.72 Example 9 Ni (AA) ₂ 4.30 Comparative Example 3 TiO (AA) ₂ 2.90 Comparative Example 4 Zr (AA) ₄ 2.05 Comparative Example 5 Cr (AA ) ₃ 2.19 Comparative Example 6 Al (AA) ₃ 1.92 Comparative Example 7 Cu (AA) ₂ 0.236 Comparative Example 8 Mn (AA) ₂ 2H ₂ O 3.39 Comparative Example 9 MoO ₂ (AA) ₂ 0.586

Example 10 A 500 ml four-necked flask equipped with a capillary, a thermometer, a raw material solution supply nozzle, a reaction solution withdrawing nozzle and a packed column with a fractionating head (Dixon packing packed about 8 stages) was used in the reactor. . 350 g of Marulotherm S solvent was charged into the reactor and placed in the mantle heater. A receiver and a reflux condenser were attached to the fractionating head, and warm water at 60 ° C was flowed.
The upper part of the reflux condenser and the receiver were connected to a vacuum line through a cold trap cooled with methanol / dry ice. A solenoid valve and a receiver were installed in the reaction liquid extraction nozzle and separately connected to a vacuum line. 1,3 in a constant temperature raw material tank of 120 ℃
After charging BUC to Marlotherm S = 1/2 weight ratio,
Iron naphthenate was dissolved to prepare an iron concentration of 48 ppm.
While maintaining the reactor liquid temperature at 250 ° C. and the system inside at 22 mmHg, the raw material liquid was supplied to the reactor at a rate of 225 g / h by a metering pump. The produced bis (isocyanatomethyl) cyclohexane (abbreviated as 1,3-BIC) and methanol were collected in a receiver and a cold trap, respectively. On the other hand, the reaction liquid was continuously withdrawn while keeping the liquid surface constant. After the reaction was started, the composition of each of the collected liquids was analyzed by gas chromatography every predetermined time. After confirming the steady state, the data was analyzed and the 1,3-BUC decomposition rate was 9
At 9.0%, the 1,3-BIC selectivity was 95.4%, and the intermediate monoisocyanate selectivity was 2.9%.

Example 11 The same procedure as in Example 10 was carried out except that cobalt naphthenate was used instead of iron naphthenate and the raw material feed rate was 150 g / h. After confirming the steady state, the data was analyzed to find that the 1,3-BUC decomposition rate was 99.9%, the 1,3-BIC selectivity was 97.7%, and the intermediate monoisocyanate selectivity was 1.7%. It was

Example 12 Example 11 was repeated except that 1,4-BUC was used in place of 1,3-BUC and nickel naphthenate was used in place of cobalt naphthenate. After checking the steady state,
As a result of analyzing the data, the 1,4-BUC decomposition rate was 99.3%, the 1,4-BIC selectivity was 94.8%, and the intermediate monoisocyanate selectivity was 2.89%.

[0040]

Industrial Applicability According to the method of the present invention, high-quality bis (isocyanatomethyl) cyclohexane containing no chlorine can be produced without handling phosgene, which is highly toxic.
Further, in the method of the present invention, unreacted dimethyl carbonate can be circulated and used as it is in the raw material system in the first reaction step in an azeotropic composition with methanol, so that the process is simplified and the utility cost can be reduced. In the second reaction step, bis (isocyanatomethyl) cyclohexane is obtained with high selectivity and high space-time yield. Therefore, the method of the present invention is an economical method for industrially producing bis (isocyanatomethyl) cyclohexane.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuuji Matsunaga 182 Shinwari, Tayuhama, Niigata City, Niigata Prefecture Mitsubishi Gas Chemical Co., Ltd. Niigata Research Center

Claims (3)

[Claims] 1. A method for producing bis (isocyanatomethyl) cyclohexane by thermally decomposing bis (methoxycarbonylaminomethyl) cyclohexane obtained by the reaction of bis (aminomethyl) cyclohexane and dimethyl carbonate, wherein (a) basic In the presence of a catalyst, the reaction is carried out in the range of 2-3.5 mol ratio of dimethyl carbonate to 1 mol of bis (aminomethyl) cyclohexane, and the unreacted dimethyl carbonate is recovered as an azeotropic composition with methanol and directly recycled to the raw material system. In the presence of the first reaction step used, (b) an inert solvent having a boiling point higher than that of bis (isocyanatomethyl) cyclohexane, and one or more metal simple substances selected from cobalt, nickel and iron or the metal compound catalyst, The bis (methoxycarbonylaminomethyl) cyclohexane obtained in the first reaction step was heated at 150-350 ° C. Bis (isocyanatomethyl) cyclohexane, characterized by comprising a second reaction step of thermally decomposing at a temperature of 1 to 500 mmHg under reduced pressure and separately recovering the produced methanol and bis (isocyanatomethyl) cyclohexane outside the system. Manufacturing method. 2. The method for producing bis (isocyanatomethyl) cyclohexane according to claim 1, wherein the basic catalyst is a metal alcoholate or a strongly basic anion exchange resin. 3. The method for producing bis (isocyanatomethyl) cyclohexane according to claim 1, wherein methyl formate is added as a promoter to the reaction between bis (aminomethyl) cyclohexane and dimethyl carbonate.